1. Field
Embodiments disclosed herein generally relate to a perpendicular magnetic recording head for recording magnetic information and a magnetic recording device employing the magnetic head.
2. Description of the Related Art
The amount of data handled by society has dramatically increased with the recent development of a highly information-based culture. Information storage devices that can input and output large volumes of data at high-speed are therefore needed, and one such device capable of this is a magnetic recording/reproduction device typified by a hard disk device. The recording density of hard disk devices continues to increase steadily due to the adoption of perpendicular recording technology and improvements therein, and attempts are currently being made to reach a density of 650 Gb/in2. However, the problem of heat fluctuation of the magnetic recording medium is gradually becoming apparent with increasing recording densities. An effective way of dealing with heat fluctuation involves increasing the anisotropy energy of the magnetic recording medium. In the case of a magnetic recording head having a small width adapted for a high recording density, an adequate recording magnetic field cannot be produced and recording is no longer possible. As a way of overcoming this problem, the distance between the magnetic recording head and recording medium is reduced, and a three-dimensional taper is provided on the main pole forming part of the magnetic recording head in order to generate a strong magnetic field.
The way of intensifying the recording magnetic field has given rise to a problem such that a leakage magnetic field is produced outside the recording track region. The main pole applies a strong magnetic field to the required recording track width, and a constricted structure known as a flare is provided. The flare part of the main pole is magnetically saturated during the recording operation so that when the distance from the recording medium is narrowed, a phenomenon occurs whereby the magnetic flux leaks directly from the flare part of the main pole to the recording medium.
FIGS. 1A-1B show a conventional magnetic head structure. FIG. 1A shows a side view of the conventional magnetic recording head 100 while FIG. 1B shows the conventional magnetic recording head 100 when viewed from the media facing surface (MFS). The conventional magnetic recording head 100 comprises: a main pole 115, a magnetic structure 116 which is magnetically coupled to the main pole 115 and increases the magnetic flux generation efficiency, a magnetic structure 113 constituting an auxiliary pole, and a coil 117. In particular, magnetic structures 112, 114 and 121 are disposed in the vertical and lateral directions of the main pole 115 and the area around the main pole is enclosed by the MFS. Here, the magnetic structures 112, 114 and 121 are referred to as shields, and in particular, 114 is referred to as the leading shield (LS), 121 is referred to as the side shield (SS) and 112 is referred to as the trailing shield (TS).
The abovementioned technology makes it possible to reduce the leakage magnetic field from the main pole to the medium, and as a result it is possible to solve the problem of incorrect magnetic data being recorded to an adjacent track. However, a problem may arise in that the quality of magnetic data written previously deteriorates in regions remote from the recording track. Deterioration of the quality of the magnetic data depends on the number of times data has been rewritten to the same track continuously, and it may no longer be possible to read out all the information after about 3,000 times. This phenomenon is known as far track interference (FTI).
FIG. 2 is a graph 200 showing an example of FTI in a magnetic recording head having flux leakage. The horizontal axis shows the position in the off-track direction (μm), with ID representing the inner diameter of a recording medium and OD representing the outer diameter of the recording medium, while the vertical axis shows the amount of reduction in the error rate (order of magnitude). For the measurements, the reproduction head was scanned after magnetic data had been written to the same track 10,000 times, and variations in the error rate in the old data were measured. The measurements were carried out using a plurality of heads (30 heads: n=30 hds). The graph 200 shows that positional offsets of 1-2 μm in both the ID and OD directions and deterioration in error rate of one order of magnitude or more were observed for essentially all of the heads. The phenomenon is a considerable obstacle to maintaining non-volatility in a magnetic recording device.
It is known to those skilled in the art that a flared head is effective for reducing the leakage magnetic field in the region of the main pole and is also effective against FTI to some extent. However, when a magnetic recording head is produced using flared head technology, the effect against FTI does not function constantly for all heads, and non-conforming articles accounting for up to about 50% are produced.
There is a need in the art for a magnetic recording device exhibiting a stable effect of restricting FTI.